Constraints on the Higgs boson properties from the effective potential

We review the constraints on Higgs boson properties from effective potential methods. In the Standard Model, the requirement of stability (or metastability) of the standard electroweak minimum puts an upper bound on the scale of new physics as a function of the Higgs mass. This upper bound is below the Planck scale if the Higgs weights $\simlt$ 130 GeV. In supersymmetric extensions of the Standard Model the former methods are useful to compute the Higgs mass spectrum, and couplings, after resumming higher loop effects. In particular, if the Higgs mass weights $\simgt$ 130 GeV, the minimal supersymmetric extension of the Standard Model will be ruled out, while its non-minimal supersymmetric extension containing singlets is only marginally allowed.